Enhancement of elastic properties by WO3 partial replacement of TeO2 in ternary (80 − x)TeO2-20PbO-xWO3 glass system

Tellurite-tungsten (80 − x)TeO2-20PbO-xWO3 (x = 0-20 mol%) glass with concurrent reduction of TeO2 and addition of WO3 was prepared by the melt-quenching method. Elastic and structural properties of the glasses were investigated by measuring both longitudinal and shear velocities using the pulse-echo overlap method at 5 MHz and Fourier Transform Infrared (FTIR) spectroscopy, respectively. Both longitudinal modulus (L) and shear modulus (G) showed a slight decrease at x = 5 mol% followed by a large and almost linear increase for x > 5 mol%. Interestingly, bulk modulus (K), Young's modulus (E) and hardness (H) recorded almost similar trends where the values showed large increase for x > 5 mol%. At x = 20 mol% the elastic moduli increased by more than 30% compared to binary 80TeO2-20PbO glass. FTIR analysis showed an increase in intensity of TeO4 assigned peaks concurrent with the decrease in intensity of TeO3 assigned peaks for x > 5 mol% which indicates an increase in number of bridging oxygen (NBO) and a decrease in non-bridging oxygen (BO), respectively. The enhancement of L, G and other related moduli for x > 5 mol% is suggested to be due to the increase in BO which caused the increase in rigidity and stiffness of the glass network. Quantitative analysis based on bulk compression and ring deformation models showed kbc/ke ratio monotonously decreased from 2.69 (x = 5 mol%) to 2.09 (x = 20 mol%) which infers that the glass system became a relatively more open 3D network for x > 5 mol% WO3 addition.